Allow exposing multiple CEA608 tracks for Transport Streams

This CL allows passing multiple formats describing CC channels to the
TS payload reader factory. As a simple usecase, ATSC can expose both
608 channels by passing a two element list with the corresponding
accessibility channels. The HLS media source can construct this list
from the EXT-X-MEDIA:TYPE="CLOSED-CAPTIONS" tags, including language
and selection flags. The interface extends without modification to
708.

Pending work:
* Multiple CC channels in HLS.
* caption_service_descriptor parsing for overriding the user's selection.
* 708 support in SEI reader.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=148030293

library/src/main/java/com/google/android/exoplayer2/extractor/mp4/FragmentedMp4Extractor.java

@@ -157,7 +157,7 @@ public final class FragmentedMp4Extractor implements Extractor {
   // Extractor output.
   private ExtractorOutput extractorOutput;
   private TrackOutput eventMessageTrackOutput;
-  private TrackOutput cea608TrackOutput;
+  private TrackOutput[] cea608TrackOutputs;
 
   // Whether extractorOutput.seekMap has been called.
   private boolean haveOutputSeekMap;
@@ -459,10 +459,12 @@ public final class FragmentedMp4Extractor implements Extractor {
       eventMessageTrackOutput.format(Format.createSampleFormat(null, MimeTypes.APPLICATION_EMSG,
           Format.OFFSET_SAMPLE_RELATIVE));
     }
-    if ((flags & FLAG_ENABLE_CEA608_TRACK) != 0 && cea608TrackOutput == null) {
+    if ((flags & FLAG_ENABLE_CEA608_TRACK) != 0 && cea608TrackOutputs == null) {
-      cea608TrackOutput = extractorOutput.track(trackBundles.size() + 1, C.TRACK_TYPE_TEXT);
+      TrackOutput cea608TrackOutput = extractorOutput.track(trackBundles.size() + 1,
+          C.TRACK_TYPE_TEXT);
       cea608TrackOutput.format(Format.createTextSampleFormat(null, MimeTypes.APPLICATION_CEA608,
           null, Format.NO_VALUE, 0, null, null));
+      cea608TrackOutputs = new TrackOutput[] {cea608TrackOutput};
     }
   }
 
@@ -1085,7 +1087,7 @@ public final class FragmentedMp4Extractor implements Extractor {
           output.sampleData(nalStartCode, 4);
           // Write the NAL unit type byte.
           output.sampleData(nalPrefix, 1);
-          processSeiNalUnitPayload = cea608TrackOutput != null
+          processSeiNalUnitPayload = cea608TrackOutputs != null
               && NalUnitUtil.isNalUnitSei(track.format.sampleMimeType, nalPrefixData[4]);
           sampleBytesWritten += 5;
           sampleSize += nalUnitLengthFieldLengthDiff;
@@ -1103,7 +1105,7 @@ public final class FragmentedMp4Extractor implements Extractor {
             nalBuffer.setPosition(MimeTypes.VIDEO_H265.equals(track.format.sampleMimeType) ? 1 : 0);
             nalBuffer.setLimit(unescapedLength);
             CeaUtil.consume(fragment.getSamplePresentationTime(sampleIndex) * 1000L, nalBuffer,
-                cea608TrackOutput);
+                cea608TrackOutputs);
           } else {
             // Write the payload of the NAL unit.
             writtenBytes = output.sampleData(input, sampleCurrentNalBytesRemaining, false);

library/src/main/java/com/google/android/exoplayer2/extractor/ts/DefaultTsPayloadReaderFactory.java

@@ -17,9 +17,13 @@ package com.google.android.exoplayer2.extractor.ts;
 
 import android.support.annotation.IntDef;
 import android.util.SparseArray;
+import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.extractor.ts.TsPayloadReader.EsInfo;
+import com.google.android.exoplayer2.util.MimeTypes;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.Collections;
+import java.util.List;
 
 /**
  * Default implementation for {@link TsPayloadReader.Factory}.
@@ -35,19 +39,36 @@ public final class DefaultTsPayloadReaderFactory implements TsPayloadReader.Fact
   public @interface Flags {
   }
   public static final int FLAG_ALLOW_NON_IDR_KEYFRAMES = 1;
-  public static final int FLAG_IGNORE_AAC_STREAM = 2;
+  public static final int FLAG_IGNORE_AAC_STREAM = 1 << 1;
-  public static final int FLAG_IGNORE_H264_STREAM = 4;
+  public static final int FLAG_IGNORE_H264_STREAM = 1 << 2;
-  public static final int FLAG_DETECT_ACCESS_UNITS = 8;
+  public static final int FLAG_DETECT_ACCESS_UNITS = 1 << 3;
-  public static final int FLAG_IGNORE_SPLICE_INFO_STREAM = 16;
+  public static final int FLAG_IGNORE_SPLICE_INFO_STREAM = 1 << 4;
 
   @Flags private final int flags;
+  private final List<Format> closedCaptionFormats;
 
   public DefaultTsPayloadReaderFactory() {
     this(0);
   }
 
+  /**
+   * @param flags A combination of {@code FLAG_*} values, which control the behavior of the created
+   *     readers.
+   */
   public DefaultTsPayloadReaderFactory(@Flags int flags) {
+    this(flags, Collections.singletonList(Format.createTextSampleFormat(null,
+        MimeTypes.APPLICATION_CEA608, null, Format.NO_VALUE, 0, null, null)));
+  }
+
+  /**
+   * @param flags A combination of {@code FLAG_*} values, which control the behavior of the created
+   *     readers.
+   * @param closedCaptionFormats {@link Format}s to be exposed by elementary stream readers for
+   *     streams with embedded closed captions.
+   */
+  public DefaultTsPayloadReaderFactory(@Flags int flags, List<Format> closedCaptionFormats) {
     this.flags = flags;
+    this.closedCaptionFormats = closedCaptionFormats;
   }
 
   @Override
@@ -74,10 +95,10 @@ public final class DefaultTsPayloadReaderFactory implements TsPayloadReader.Fact
         return new PesReader(new H262Reader());
       case TsExtractor.TS_STREAM_TYPE_H264:
         return isSet(FLAG_IGNORE_H264_STREAM) ? null
-            : new PesReader(new H264Reader(new SeiReader(), isSet(FLAG_ALLOW_NON_IDR_KEYFRAMES),
+            : new PesReader(new H264Reader(buildSeiReader(), isSet(FLAG_ALLOW_NON_IDR_KEYFRAMES),
                 isSet(FLAG_DETECT_ACCESS_UNITS)));
       case TsExtractor.TS_STREAM_TYPE_H265:
-        return new PesReader(new H265Reader(new SeiReader()));
+        return new PesReader(new H265Reader(buildSeiReader()));
       case TsExtractor.TS_STREAM_TYPE_SPLICE_INFO:
         return isSet(FLAG_IGNORE_SPLICE_INFO_STREAM)
             ? null : new SectionReader(new SpliceInfoSectionReader());
@@ -88,6 +109,11 @@ public final class DefaultTsPayloadReaderFactory implements TsPayloadReader.Fact
     }
   }
 
+  private SeiReader buildSeiReader() {
+    // TODO: Add descriptor parsing to detect channels automatically.
+    return new SeiReader(closedCaptionFormats);
+  }
+
   private boolean isSet(@Flags int flag) {
     return (flags & flag) != 0;
   }

library/src/main/java/com/google/android/exoplayer2/extractor/ts/SeiReader.java

@@ -21,25 +21,45 @@ import com.google.android.exoplayer2.extractor.ExtractorOutput;
 import com.google.android.exoplayer2.extractor.TrackOutput;
 import com.google.android.exoplayer2.extractor.ts.TsPayloadReader.TrackIdGenerator;
 import com.google.android.exoplayer2.text.cea.CeaUtil;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.ParsableByteArray;
+import java.util.List;
 
 /**
  * Consumes SEI buffers, outputting contained CEA-608 messages to a {@link TrackOutput}.
  */
 /* package */ final class SeiReader {
 
-  private TrackOutput output;
+  private final List<Format> closedCaptionFormats;
+  private final TrackOutput[] outputs;
+
+  /**
+   * @param closedCaptionFormats A list of formats for the closed caption channels to expose.
+   */
+  public SeiReader(List<Format> closedCaptionFormats) {
+    this.closedCaptionFormats = closedCaptionFormats;
+    outputs = new TrackOutput[closedCaptionFormats.size()];
+  }
 
   public void createTracks(ExtractorOutput extractorOutput, TrackIdGenerator idGenerator) {
-    idGenerator.generateNewId();
+    for (int i = 0; i < outputs.length; i++) {
-    output = extractorOutput.track(idGenerator.getTrackId(), C.TRACK_TYPE_TEXT);
+      idGenerator.generateNewId();
-    output.format(Format.createTextSampleFormat(idGenerator.getFormatId(),
+      TrackOutput output = extractorOutput.track(idGenerator.getTrackId(), C.TRACK_TYPE_TEXT);
-        MimeTypes.APPLICATION_CEA608, null, Format.NO_VALUE, 0, null, null));
+      Format channelFormat = closedCaptionFormats.get(i);
+      String channelMimeType = channelFormat.sampleMimeType;
+      Assertions.checkArgument(MimeTypes.APPLICATION_CEA608.equals(channelMimeType)
+          || MimeTypes.APPLICATION_CEA708.equals(channelMimeType),
+          "Invalid closed caption mime type provided: " + channelMimeType);
+      output.format(Format.createTextSampleFormat(idGenerator.getFormatId(), channelMimeType, null,
+          Format.NO_VALUE, channelFormat.selectionFlags, channelFormat.language,
+          channelFormat.accessibilityChannel, null));
+      outputs[i] = output;
+    }
   }
 
   public void consume(long pesTimeUs, ParsableByteArray seiBuffer) {
-    CeaUtil.consume(pesTimeUs, seiBuffer, output);
+    CeaUtil.consume(pesTimeUs, seiBuffer, outputs);
   }
 
 }

library/src/main/java/com/google/android/exoplayer2/text/cea/CeaUtil.java

@@ -35,14 +35,14 @@ public final class CeaUtil {
 
   /**
    * Consumes the unescaped content of an SEI NAL unit, writing the content of any CEA-608 messages
-   * as samples to the provided output.
+   * as samples to all of the provided outputs.
    *
    * @param presentationTimeUs The presentation time in microseconds for any samples.
    * @param seiBuffer The unescaped SEI NAL unit data, excluding the NAL unit start code and type.
-   * @param output The output to which any samples should be written.
+   * @param outputs The outputs to which any samples should be written.
    */
   public static void consume(long presentationTimeUs, ParsableByteArray seiBuffer,
-      TrackOutput output) {
+      TrackOutput[] outputs) {
     while (seiBuffer.bytesLeft() > 1 /* last byte will be rbsp_trailing_bits */) {
       int payloadType = readNon255TerminatedValue(seiBuffer);
       int payloadSize = readNon255TerminatedValue(seiBuffer);
@@ -62,8 +62,12 @@ public final class CeaUtil {
         // Each data packet consists of 24 bits: marker bits (5) + cc_valid (1) + cc_type (2)
         // + cc_data_1 (8) + cc_data_2 (8).
         int sampleLength = ccCount * 3;
-        output.sampleData(seiBuffer, sampleLength);
+        int sampleStartPosition = seiBuffer.getPosition();
-        output.sampleMetadata(presentationTimeUs, C.BUFFER_FLAG_KEY_FRAME, sampleLength, 0, null);
+        for (TrackOutput output : outputs) {
+          seiBuffer.setPosition(sampleStartPosition);
+          output.sampleData(seiBuffer, sampleLength);
+          output.sampleMetadata(presentationTimeUs, C.BUFFER_FLAG_KEY_FRAME, sampleLength, 0, null);
+        }
         // Ignore trailing information in SEI, if any.
         seiBuffer.skipBytes(payloadSize - (10 + ccCount * 3));
       } else {